Distribution. Florida: native; north and central peninsula, west to central panhandle. General: south Ohio, Kentucky-Illinois west to southeast Kansas, south to central Florida, Texas, Louisiana, and Mexico.

Toxicity

Irritant compounds (histamines and acetocholines) that cause reddening and intense itching fill the stiff, hypodermic-needle-like stinging hairs on the stem and leaves (Fig. 4). When the tip of the brittle, tubular hair is broken, pressure on the bulbous hair base injects the irritants into the skin. The usual reaction, reddening and intense itching, is usually of short duration, although sensitive individuals may experience some swelling and burning. Washing the affected area or immediate application of baking soda paste soothes the stinging sensation for most people.

Economic Uses

None for this species. Related species of Urtica are used in herbal medicine and as an edible, spinach-like potherb (after boiling); extracts of the stinging compounds show promise as treatment for inflammatory conditions, such as arthritis.

Comments

The habit of U. chamaedryoides varies according to the environmental conditions: plants in shady areas tend to have longer, weaker stems with larger, more coarsely toothed leaves and looser flower clusters (Fig. 1), while plants in more exposed areas are much smaller with more compact flower clusters (Fig. 5).

The unrelated Cnidoscolusstimulosus (bull-nettle, stinging-nettle, tread-softly, finger-rot, Fig. 6; Euphorbiaceae, spurge family), a common Florida plant, also has stinging hairs but is characterized by conspicuous white flowers and large, lobed leaves. A plant fact sheet for this species is also available.

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U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.